Jack Russels.
Have had many.. and out of all the terriers they are the ones I would pick.
Knew a lady quite well who did a terrier rescue.. and I'm sorry to say all the Rat Terriers that passed through their were the yappiest, hard to calm down dogs. I'm sure not every one is that way, but a good many are.
Love our Jacks a whole bunch. My current puppy is kind of insane.. but he really does well with the chickens. I brooded the chicks in my room and he was in here at night with them.. never bothered them or really looked at them like they are prey. Although Jacks are very, very prey orientated. They love to hunt, and it's hard to keep them from it. Mine being great with the chickens has more to do, I think, with him being young and introduced to them at an early age... so hes well used to the sound, smell, and sight of them.
I would never trust him completely with them though, never. Our Jacks in the past have been such ferocious hunters. They do have very energetic personalities.. they need to be kept entertained... but with most they will also have nice periods of calm where you can snuggle.
Rosie used to do frisbee competitions.. she jumps so high (measured once at 5 feet)... an announcer once nick-named her 'Air-Rosie'... you can see a pic of her and others on my BYC page. My Tilly (miss her) was a wonderful little girl... she was always snuggling with me... and when I worked on the farm, she would follow me around not more than 4 feet behind me all day, ride in the cart out to feed the horses.. and help me muck out by way of her stomach
She was my once-in-a-lifetime dog.
For all that though.. Jacks aren't for everyone. My current puppy is just a crazy-head, very smart, but crazy.
Other terriers can be difficult too. After all your research, It is advisable to ask the breeder to see the parent dogs and spend a goodly time observing and interacting with them to see if the breed (and line) is a fit for you.